Learning from Swedish Home Building Part 3

This video piece is about how Sweden has modified the Western Platform Framing method for better energy performance in residential construction. We call this modified framing method Swedish Platform Framing.

This video is quite long, and we apologize about that. If we figure out how to say all this in a shorter video we'll produce a new version. In this video we make a very breif review of the history of stud framing systems - Balloon Framing and Western Platform Framing. Then we proceed to look in detail at the differences between Western and Swedish Platform framing.

AS with the USA New Wall, the walls shown in this video use Stone Wool insulation rather than fiberglass. We mention in the video that this is because Stone Wool offers higher insulation values - R23 for 2x6 stud spaces, and R30 for 2x8 stud spaces. We also mention that it allows for better installations. You can read a detailed article about why this is so on our blog:http://blog.lamidesign.com/2012/01/what-you-don-know-about-mineral-wool.html

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I've had these same questions repeatedly, and perhaps many of your questions would be answered by reading the detailed pages on USA New Wall and Swedish Platform Framing.

But for the benefit of everybody here I'll respond breifly to each of your questions:

Dismissing Advanced Framing (AF): Yes, I do emphatically dismiss it. Aside from a few green builders and the publication of applications of AF on the DOE web site, I see little to no uptake of this.

I agree that Swedish Platform Framing (SPF) is more different than AF from ordinary Western Platform Frame (WPF), however it is easier to implement for builders because it does not impose a 24" grid, and it does not require a redesign of the house plans the builder is working with. Granted, with AF you could put the windows where the plans say and not redesign, but then you introduce more wood, more off grid studs, which basically undermines the premise of the system.

SPF is not about the grid, and it is not about using less wood. Its about configuring the framing for the best energy performance. In this regard you are wrong. SPF eliminates the bulk of horizontal thermal bridges from the wall and provides a better condition for insulation framing at the floor levels. It is head and shoulders better than AF in this regard. If you do not see that, then you do not understand what you are looking at.

Beyond the framing differences, the exterior insulation and interior wiring chase insulation are integral to better performance. Using these with AF would certainly improve its performance as well.

I can make no sense of your vapor barrier comments. The USA New Wall locates the variable permeability vapor retarder at the surface of the studs, behind the wiring chase. There is no problem with that location. You suggest it should be right against the drywall. No, this is precisely where it should not be, because this is where it would receive large holes for every electrical outlet and switch box in the house. And yes, I've read recommendations to seal these electrical boxes - that seems like folly to me. It is located behind the wiring space to avoid these holes, and also so it can provide the primary air sealing layer for the house.

Why not eliminate it?

Once you eliminate the vapor retarder/air tight layer now you need to establish your air tight layer elsewhere. Where? At the drywall - fraught with holes from electrical work as discussed before. At the sheathing? Ok, but now you are going to be inviting warm winter air into your wall cavity via all the holes in the drywall where you can possibly have it condense on the framing and backside of the sheathing.

Ok - so you spray foam the inside. Sure, go ahead, that works, and many green builders have advised that. But back to the real world. Builders of the country don't do spray foam. They stuff batts. Now you are asking them to bring in a new subcontractor, somebody they don't know and have not worked with before, blah blah blah. And you are adding a new step to their sequence, and they don't know how long this will take them or how much it will cost or how to price it. I'm not saying all these excuses are valid, I'm saying they will prevent it from happening.

So I don't want to discount your recommendations. I think they are fine, you can build a great house that way. But the approaches you described have been bandied about for sometime now and they've not changes much. I'm interested in ideas that the average builder can take up and try. That's why all of this is introduced in stages.

I wouldn't dismiss the American advanced wall framing so quickly. Stating that it has not be widely adopted has no relevance to its efficiency. Without doing an energy model I would guess that thermal bridging losses compared to the Swedish frame are similar, and any small differences would be dramatically reduced by an exterior insulation. Also the entire wiring chase would be unnecessary if a spray in wall cavity insulation is used. From a practicality standpoint moving Americans to an advanced wall frame would be easier than the Swedish system.

Vapor barriers should not be installed on the inside of a walls assemblies, it should be as close as possible to the interior or exterior wall based on climate zone. The Certainteed vapor barrier seems silly, it only works as a vapor barrier when there is no vapor load and becomes vapor permeable when there is a load. Why not just eliminate the vapor barrier, the wall would work the same. In terms of vapor loads air sealing is the critical factor as most moisture is transported by convection vs. diffusion. I would recommend using a wall spray insulation that doesn't require a vapor barrier and using a vapor retardant wall paint if demanded by the building inspector.

Another major consideration is the meticulous attention to air sealing the frame as it is erected, something I'm sure the Swedish are very good at.